Scanning optical system

ABSTRACT

A scanning optical system is used to re-form an original image on a CCD line sensor. The optical system has an object side lens unit, a mirror and an image side lens unit. The object side lens unit condenses light from the object. The mirror is arranged between the object side lens to deflect the light having passed through the object side lens unit for scanning. An exit pupil of the object side lens unit coincide with an entrance pupil of the image side lens unit.

RELATED APPLICATIONS

The present application is a divisional application of U.S. Ser. No.08/806,025 filed on Feb. 24, 1997, now U.S. Pat. No. 6,128,120.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a scanning optical system, for example,to a scanning optical system for use in apparatuses such as filmscanners capable of high-speed image capture.

2. Description of the Prior Art

Various types of film scanners have been proposed. Of them, a filmscanner of mirror-scan type is well known. The mirror-scan type filmscanner is constituted of a line sensor (e.g. line charge coupled device(CCD)) having its light receiving devices arranged in a sub scanningdirection, a scanning optical system for imaging film images on the linesensor, and a mirror being swingingly rotated for main scanning.

The above-described type of film scanner faces a problem that since thefilm image plane to be scanned is flat, when it is scanned, the opticalpath length between the mirror and the scanned image plane changes asthe mirror rotates. To solve this problem, Japanese Published PatentApplication No. S62-20526 discloses a scanning apparatus which achieveshigh-speed scanning of flat image planes without causing any curvatureby disposing a rotationally asymmetrical imaging optical system having adesirable Petzval sum between the mirror and the scanned image plane tocorrect the optical path length.

However, the imaging optical system used in the scanning apparatus ofJapanese Published Patent Application No. S62-20526 is an expensiveoptical system having a surface configuration which is difficult tomanufacture, so that the cost of the scanning apparatus rises. Inaddition, since it is inevitable to use a large-size mirror, it isdifficult to rotate the mirror at high speed, so that it takes tenseconds to several minutes to capture the image of one frame of thefilm.

In the scanning optical system of mirror-scan type, the mirror isswingingly rotated for scanning, so that a biased load is imposed on thebearing of the mirror every time scanning is performed. As a result, thebearing of the mirror is biasedly worn or partially out of oil. Inaddition, the driving apparatus (e.g. galvanic apparatus) for swinginglyrotating the mirror is expensive and is a cause of the complication ofthe scanning apparatus.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a scanning opticalsystem enabling high-speed scanning without causing any curvature evenif the surface to be scanned is flat, and reducing the biased loadimposed on the bearing of the mirror without increasing the complexityand cost of the scanning apparatus.

To achieve the above-mentioned object, a scanning optical systemaccording to one aspect of the present invention is provided with anobject side lens unit, a deflector for deflecting light passing throughthe object side lens unit to perform scanning for taking in a primaryimage formed on an object side surface, said deflector being disposed ina vicinity of an exit pupil of the object side lens unit, and an imageside lens unit for focusing on an image side surface both axial andoff-axial rays with respect to a sub-scanning direction, said image sidelens unit being provided so that an entrance pupil thereof substantiallycoincides with an exit pupil of the object side lens unit.

In a scanning optical system according to another aspect of the presentinvention, a primary image formed on an object side surface is projectedon an image plane as a secondary image by a lens system by performingscanning, and the scanning is performed by moving the entire lens systemrelatively to the object side surface and to the image plane andvertically to an optical axis of the lens system.

BRIEF DESCRIPTION OF THE DRAWINGS

This and other objects and features of this invention will become clearfrom the following description, taken in conjunction with the preferredembodiments with reference to the accompanied drawings in which:

FIG. 1 is a perspective view schematically showing a basic arrangementof first to fifth embodiments of the present invention;

FIG. 2 is a view of assistance in explaining the relationship betweenthe image plane and the projection methods of an object side lens unitin the embodiments of FIG. 1;

FIG. 3 shows the lens arrangement of the first embodiment at a mirrorrotation angle θ of 45 degrees;

FIG. 4 shows the lens arrangement of the first embodiment at a mirrorrotation angle θ of 48.5 degrees;

FIG. 5 shows the lens arrangement of the first embodiment at a mirrorrotation angle θ of 41.5 degrees;

FIG. 6 shows the lens arrangement of the second embodiment at a mirrorrotation angle θ of 45 degrees;

FIG. 7 shows the lens arrangement of the second embodiment at a mirrorrotation angle θ of 48.5 degrees;

FIG. 8 shows the lens arrangement of the second embodiment at a mirrorrotation angle θ of 41.5 degrees;

FIG. 9 shows the lens arrangement of the third embodiment at a mirrorrotation angle θ of 45 degrees;

FIG. 10 shows the lens arrangement of the third embodiment at a mirrorrotation angle θ of 48.5 degrees;

FIG. 11 shows the lens arrangement of the third embodiment at a mirrorrotation angle θ of 41.5 degrees;

FIG. 12 is a cross-sectional view in the sub scanning direction showingthe lens arrangement of the fourth embodiment at a high magnificationcondition and at a low magnification condition;

FIG. 13 is a cross-sectional view in the main scanning direction showingthe lens arrangement of the fifth embodiment at a mirror rotation angleθ of 45 degrees;

FIG. 14 is a cross-sectional view in the main scanning direction showingthe lens arrangement of the fifth embodiment at a mirror rotation angleθ of 48.5 degrees;

FIG. 15 is a cross-sectional view in the main scanning direction showingthe lens arrangement of the fifth embodiment at a mirror rotation angleθ of 41.5 degrees;

FIGS. 16A to 16C schematically show the arrangement of a scanningapparatus embodying the present invention;

FIGS. 17A to 17C schematically show the arrangement when film images arecaptured at unity magnification by the scanning apparatus of FIGS. 16Ato 16C;

FIG. 18 shows the lens arrangement of a lens unit of a sixth embodimentused in the scanning apparatus of FIGS. 16A to 16C and 17A to 17C;

FIG. 19 shows the lens arrangement of a lens unit of a seventhembodiment used in the scanning apparatus of FIGS. 16A to 16C and 17A to17C; and

FIG. 20 shows the lens arrangement of a lens unit of an eighthembodiment used in the scanning apparatus of FIGS. 16A to 16C and 17A to17C.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a scanning optical system embodying the present inventionwill be described with reference to the drawings in which the X-axis,the Y-axis and the Z-axis are axes perpendicular to one another. FIG. 1shows a basic arrangement of a scanning optical system common to firstto fifth embodiments of the present invention. The scanning opticalsystem is a mirror-scan type scanning optical system having, from theimage side, an image side lens unit Gr1, a mirror M and an object sidelens unit Gr2. On the object side of the scanning optical system, a filmimage plane 1 is disposed in a fixed position during the image capture.On the image side of the scanning optical system, a line CCD 3 and aprism (or a filter) 2 are disposed. The prism 2 which is a colorseparation prism used for three-plate color separation is unnecessarywhen color separation is not performed.

The object side lens unit Gr2 (in this part of the lens system, theoptical axis is in parallel with the X-axis) condenses light from thefilm image plane 1. In FIG. 1, RB is an axial light in the main and subscanning directions, RA is an off-axial light at an object height Z(+)and an image height Z′(−) in the sub scanning direction, and RC is anoff-axial light at an object height Z(−) and an image height Z′(+) inthe sub scanning direction. The plane-form mirror M performs mainscanning of the film image plane 1 by deflecting light having passedthrough the object side lens unit Gr2. The deflection is performed byrotating the mirror M. The main scanning of the film image plane 1 isperformed in the direction of the Y-axis. The image side lens unit Gr1(in this part of the lens system, the optical axis is in parallel withthe Y-axis) images on the image side surface of the line CCD 3 both theaxial light and the off-axial light in the sub scanning direction (thedirection of the Z-axis) deflected by the mirror M. The image formed onthe image side surface of the lines CCD 3 is an image in the subscanning direction (the direction of the Z-axis) on the film image plane1 and is captured line by line as image information by the line CCD 3.

The lens elements included in the object side lens unit Gr2 have theiry-z cross sections formed circular so that the luminous flux is coveredwith respect to both the Y- and Z-axes. On the other hand, the lenselements included in the image side lens unit Gr1 have their x-z crosssections formed elongated along the Z-axis because the luminous flux isnecessarily covered. only with respect to the sub scanning direction(the direction of the Z-axis) which is the direction in which the lightreceiving devices of the line CCD 3 are arranged. By thus forming theimage side lens unit Gr1 to be elongated, the space in the scanningapparatus is saved.

While the line CCD 3 is used as the image capturing portion in thepresent scanning optical system, another type of line sensor may be usedas the image capturing portion instead of the line CCD 3, or aphotoreceptor drum may be used as the image capturing portion. In a casewhere a photoreceptor drum is used, the photoreceptor drum is disposedso that its generatrix is in parallel with the sub scanning direction,and the rotation of the photoreceptor drum is synchronized with therotation of the mirror M.

While the present scanning optical system is applied to a film scanner,the scanning optical system of the present invention is applicable toother scanning apparatuses. For example, instead of the line CCD 3, anapparatus (e.g. a light emitting diode (LED) array or atransmission-type liquid crystal display (LCD) panel) may be disposedwhich emits light including image information, and instead of the filmimage plane 1, a light receiving apparatus (e.g. an area CCD or aplane-form photoreceptor) may be provided which receives, reads andrecords light including image information. In this case, the image sidelens unit Gr1 is the object side lens unit and the object side lens unitGr2 is the image side lens unit.

Next, image distortions will be described which are caused by differentprojection methods of the object side lens unit Gr2. (A) of FIG. 2 showsa film image on the film image plane 1 (FIG. 1). Ymax is a main scanningrange and Zmax is a sub scanning range. (B) to (D) of FIG. 2 show imagesof the film image formed in the position of the image side surface ofthe line CCD 3 when the main scanning of the film image plane 1 isperformed by rotating the mirror M at a uniform angular velocity by useof object side lens units Gr2 of various projection methods. The imageshown in (B) of FIG. 2 is obtained when an fθ lens is used as the objectside lens unit Gr2. The image shown in (C) of FIG. 2 is obtained when anfsinθ lens is used as the object side lens unit Gr2. The image shown in(D) of FIG. 2 is obtained when an ftanθ lens is used as the object sidelens unit Gr2.

According to the fθ system ((B) of FIG. 2), since the intervals in themain scanning direction (the direction of the Y-axis) are the same, itis unnecessary to correct the rotation speed of the mirror M. However,it is necessary to two-dimensionally correct the image with respect toboth the main and sub scanning directions (the directions of Y- andZ-axes). According to the fsinθ system ((C) of FIG. 2) and the ftanθsystem ((D) of FIG. 2), although it is necessary to correct the rotationspeed of the mirror M since the intervals in the main scanning directionare different, the necessary image correction is one-dimensional.According to the fθ system and the fsinθ system, however, sincedistortion is caused which is curved; in the main scanning direction(the direction of the Y-axis), it is difficult to project on the imageside surface of the line CCD 3 all the line images on the correspondingfilm image plane 1.

In the present scanning optical system, an ftanθ optical system is usedas the object side lens unit Gr2. In the case of the ftanθ system, whenthe main scanning of the film image plane 1 is performed by deflectingthe light with the mirror M, the optical path in the object side lensunit Gr2 changes and the projection changes accordingly. That is,according to the projection method of the ftanθ system, as shown in (D)of FIG. 2, the farther the light deflected by the mirror M is away fromthe optical axis in the main scanning direction (the direction of theY-axis), the farther the light incident on the object side lens unit Gr2is away from the optical axis than it should be, so that the image isdistorted in the main scanning direction. The change in projection inthe main scanning direction is eliminated by correcting the speed ofscanning by the mirror M. Therefore, in the present scanning opticalsystem, the image is prevented from being distorted in the main scanningdirection by increasing the main scanning speed as the light deflectedby the mirror M becomes farther away from the optical axis. High-speedscanning without any distortion in the main scanning direction is thusenabled.

On the other hand, in the sub scanning, the farther the light deflectedby the mirror M is away from the optical axis in the main scanningdirection, the farther the light, incident on the object side lens unitGr2 is away from the optical axis than it should be, so that the imageis distorted in the sub scanning direction. The change in projection inthe sub scanning direction is eliminated by one-dimensionally correctingthe image with respect to the sub scanning direction. Therefore, in thepresent scanning optical system, the distortion of the image in the subscanning direction is electrically corrected by processing the capturedimage. The above-described correction of the image with respect to thesub scanning direction is easily made since it is a correction withrespect to the direction in which the light receiving devices of theline CCD 3 are arranged (i.e. the direction of the Z-axis). High-speedscanning without any distortion in the sub scanning direction is thusenabled.

In the present scanning optical system, the deflection for the mainscanning is performed by rotating the mirror M like in conventionalmirror-scan type scanning optical systems. However, the mirror M is notonly swingingly rotated. That is, since a space which enables a360-degree rotation of the mirror M is provided between the object sidelens unit Gr2 and the image side lens unit Gr1, by rotating the mirror M360 degrees, the bearing of the mirror M is prevented from continuouslyreceiving a biased load. The 360-degree rotation of the mirror M may bemade, for example, every main scanning, every time the main scanning isperformed a predetermined number of times, or only at start-up (i.e.when the power of the scanning apparatus is turned on).

By thus reducing the biased load imposed on the bearing of the mirror M,the bearing of the mirror M is prevented from being biasedly worn orfrom being partially out of oil. In addition, since it is unnecessary touse a driving apparatus (e.g. galvanic apparatus) for swinginglyrotating the mirror M and the 360-degree rotation of the mirror M ismade with a driving apparatus (e.g. driving apparatus comprising a DCmotor) which is less expensive and simpler in structure, the costreduction and the simplification of the structure of the scanningapparatus are achieved.

Next, the structure of the scanning optical system shown in FIG. 1 willbe described in detail with reference to the first to third embodiments.FIGS. 3 to 5, FIGS. 6 to 8, and FIGS. 9 to 11 show x-y cross sectionscorresponding to the first to third embodiments, respectively. FIGS. 3,6 and 9 show the optical path at a mirror rotation angle (i.e. mirrorswing angle) θ of 45 degrees (at this time, the object height Y=0).FIGS. 4, 7 and 10 show the optical path at a mirror rotation angle θ of48.5 degrees. FIGS. 5, 8 and 11 show the optical axis at a mirrorrotation angle θ of 41.5 degrees. In the lens arrangements of FIGS. 3, 6and 9, Si (i=1, 2, 3, . . . ) represents an ith surface counted from theobject (film image plane 1) side.

First Embodiment

In the first embodiment shown in FIGS. 3 to 5, the image side lens unitGr1 and the object side lens unit Gr2 each include nine rotationallysymmetrical spherical lens elements, and adopts a symmetrical structurewith respect to the mirror M which is advantageous to aberrationcorrection. The image side lens unit Gr1 has its x-z cross sectionformed elongated. As described above, the space in the scanningapparatus is saved by forming the image side lens unit Gr1 to beelongated. In FIGS. 3 to 5, the object height Y corresponding to a rangeof θ=45 degrees (FIG. 3) ±3.5 degrees is the main scanning range Ymax.

The first embodiment is arranged so that the exit pupil of the objectside lens unit Gr2 and the entrance pupil of the image side lens unitGr1 substantially coincide with each other. That the exit pupil of theobject side lens unit and the entrance pupil of the image side lens unitsubstantially coincide with each other means that the exit pupil of theobject side lens unit and the entrance pupil of the image side lens unitwhich lens units have substantially the same pupil diameter and arelocated substantially in the same position. In accordance with thisdefinition, the arrangement where the exit pupil of the object side lensunit and the entrance pupil of the image side lens unit coincide witheach other in an optical system where the optical axes of the objectside lens unit and the image side lens unit coincide with each otherwill be described in further detail with respect to the following fourcases in the order presented: (1) a case where the two pupils havesubstantially the same pupil diameter but are not located substantiallyin the same position; (2) a case where the two pupils are locatedsubstantially in the same position but do not have substantially thesame pupil diameter; (3) a case where the two pupils have differentpupil diameters and are located in different positions; and (4) the caseof the first embodiment.

In the case (1), since the two pupils are not located substantially inthe same position, for example when the axial light exits from theobject side lens unit as divergent light, part of the axial light cannotpass through the entrance pupil of the image side lens unit, so thatthere is a loss in the quantity of the light. Conversely, when the axiallight exits from the object side lens unit as convergent light, the areaof the image side lens unit through which no light passes increases, sothat the overall size of the optical system increases. In addition, whenthe exit pupil of the object side lens unit and the entrance pupil ofthe image side lens unit are not located substantially in the sameposition, not all of the off-axial light (i.e. light having an imageheight) having passed through the exit pupil of the object side lensunit can be incident on the entrance pupil of the image side lens unit.

In the case (2), since the exit pupil of the object side lens unit andthe entrance pupil of the image side lens unit are located substantiallyin the same position, of the pupils, the one having a smaller diametervirtually restricts the light. Therefore, when the exit pupil of theobject side lens unit has a greater diameter than the entrance pupil ofthe image side lens unit, not all of the light from the object side canbe transmitted to the image side irrespective of whether the light isaxial or off-axial. Conversely, when the entrance pupil of the imageside lens unit has a greater diameter than the exit pupil of the objectside lens unit, the area of the image side lens unit through which nolight passes increases, so that the overall size of the optical systemincreases.

In the case (3), the exit pupil diameter of the object side lens unitand the entrance pupil diameter of the image side lens unit canappropriately be set so that the axial light is all transmitted from theobject side lens unit to the image side lens unit. In this case,however, similarly to the case (1), if the exit pupil of the object sidelens unit and the entrance pupil of the image side lens unit are notlocated substantially in the same position, not all of the off-axiallight having passed through the exit pupil of the object side lens unitcan be incident on the entrance pupil of the image side lens unit.

On the contrary, in the case (4) of the first embodiment, since the exitpupil of the object side lens unit Gr2 and the entrance pupil of theimage side lens unit Gr1 substantially coincide with each other, theaxial light and the off-axial light having passed through the exit pupilof the object side lens unit Gr2 are all incident on the entrance pupilof the image side lens unit Gr1 and are all transmitted from the objectside lens unit Gr2 to the image side lens unit Gr1. Consequently, theaxial light and the off-axial light in the sub scanning directiondeflected by the mirror M are both imaged on the image side surface ofthe line CCD 3 by the image side lens unit Gr1.

For example, in a laser scanning optical system for use in printers,since the axial light and the off-axial light are both used in the mainscanning direction, the mirror is disposed in the vicinity of theentrance pupil of the lens unit located on the image side. However,since the off-axial light is not used in the sub scanning direction(i.e. the off-axial light does not have an image height in the subscanning direction), it is unnecessary that the pupils of the lens unitscorresponding to the object side lens unit Gr2 and the image side lensunit Gr1 of the first embodiment coincide with-each other. On thecontrary, in the first embodiment, since the axial light and theoff-axial light in the sub scanning direction deflected by the,mirror Mare both imaged on the image side surface by the image side lens unitGr1 (i.e. have an image height in the sub scanning direction), if theexit pupil of the object side lens unit Gr2 and the entrance pupil ofthe image side lens unit Gr1 do not substantially coincide with eachother, not all of the off-axial light having passed through the exitpupil of the object side lens unit Gr2 can be incident on the entrancepupil of the image side lens unit Gr1.

By thus arranging the lens system so that the exit pupil of the objectside lens unit Gr2 and the entrance pupil of the image side lens unitGr1 substantially coincide with each other, the object side lens unitGr2 and the image side lens unit Gr1 constitute one lens system having acommon pupil. The object side lens unit Gr2 and the image side lens unitGr1 each include only rotationally symmetrical spherical lens elementsand have the field of curvature excellently corrected. Therefore, nocurvature is caused in the image plane with respect to the entirescanning optical system. Since correction of field of curvature iseasily made for each of the object side lens unit Gr2 and the image sidelens unit Gr1, it is unnecessary to use an optical system having acomplicated surface configuration, and the object side lens unit Gr2 andthe image side lens unit Gr1 are formed only of rotationally symmetricalspherical lens elements which are inexpensive and easy to manufacture.By thus forming the object side lens unit Gr2 and the image side lensunit Gr1 of rotationally symmetrical spherical lens elements which areinexpensive and easy to manufacture, the cost reduction of the scanningapparatus is achieved. In addition, since the scanning optical systemincluding only spherical lens elements is simple in structure, therotation speed of the mirror M is readily increased. As a result, theimage of one frame of the 135 film is captured in approximately 0.2 toone second.

The mirror M is small compared with ones provided in conventionalscanning optical systems. However, since the mirror M is disposed in thevicinity of the pupils substantially coinciding with each other asdescribed above, the light is all transmitted from the object side lensunit Gr2 to the image side lens unit Gr1. When the light is deflected bythe mirror M disposed in the vicinity of the coinciding pupils, sincethe field of curvature of the lens units Gr1 and Gr2 is excellentlycorrected, no curvature is caused in the image plane formed on the imageside surface of the line CCD 3. Consequently, even if the film imageplane 1 to be scanned is flat, high-speed scanning without any curvatureis achieved. The mirror M has only its central portion formed reflectiveand has the peripheral portion formed light-proof (or transmissive).Consequently, the mirror M functions as an aperture diaphragm forrestricting the incident luminous flux according to the size andconfiguration of the reflective portion. While the present scanningoptical system is arranged so that parallel light is incident on themirror M, it may be arranged so that convergent or divergent light isincident on the mirror M.

When the main scanning of the film image plane 1 is performed by themirror M, the optical path in the object side lens unit Gr2 changes.That is, in the main scanning direction, even if the light incident onthe object side lens unit Gr2 is off-axial light, the light is incidenton the image side lens unit Gr1 as axial light. However, since theobject side lens unit Gr2 and the image side lens unit Gr1 each satisfyan image quality as an independent front aperture lens system with themirror M functioning as the aperture diaphragm, a sufficient imagequality is obtained with the entire scanning optical system.

Second Embodiment

In the second embodiment shown in FIGS. 6 to 8, the image side lens unitGr1 and the object side lens unit Gr2 each include nine rotationallysymmetrical spherical lens elements, and adopts a symmetrical structurewith respect to the mirror M which is advantageous to aberrationcorrection. This embodiment is suitable for color separation because theprism 2 is provided on the side of the line CCD 3.

In this embodiment, the exit pupil of the object side lens unit Gr2 andthe entrance pupil of the image side lens unit Gr1 substantiallycoincide with each other like in the above-described first embodimentand the same advantages are obtained. Since the object side lens unitGr2 and the image side lens unit Gr1 each satisfy an image quality as anindependent front aperture lens system with an aperture diaphragm Afunctioning as a front aperture, a sufficient image quality is obtainedwith the entire scanning optical system like in the first embodiment.

The second embodiment is characterized in that the aperture diaphragm Ais disposed in the vicinity of the substantially coinciding pupils andthe mirror M is disposed between the object side lens unit Gr2 and theaperture diaphragm A. In the case where the main scanning of the filmimage plane 1 is performed by deflecting the light with the mirror M, ifthe mirror M functions as the aperture diaphragm for restricting theluminous flux like in the first embodiment, the projection changes witha change in angle between the mirror M and the luminous flux. Thequantity of the light incident on the image side lens unit Gr1 changeswith the change of the projection. For example, the quantity of thelight received by the mirror M increases as the mirror rotation angle θincreases, and conversely, the quantity of the light received by themirror M decreases as the mirror rotation angle θ decreases.Consequently, nonuniformity of light quantity is caused in the imagecaptured by the line CCD 3.

According to the arrangement of the second embodiment, since a whollyreflective mirror M is disposed between the object side lens unit Gr2and the aperture diaphragm A, the luminous flux is restricted not by themirror M but by the aperture diaphragm A, so that the quantity of thelight incident on the image side lens unit Gr1 is uniform. As a result,the illuminance distribution (i.e. the illuminance distribution on theimage side surface of the line CCD 3) is prevented from deteriorating.In the case where the aperture diaphragm A is disposed between theobject side lens unit Gr2 and the mirror M, the luminous flux iseclipsed in the main scanning.

The image side lens unit Gr1 is substantially telecentric to the imageside and is therefore suitable for an arrangement where a line sensorsuch as a multi-plate (e.g. three-plate) line CCD is used as the imagecapturing portion. This is because the more telecentric the image sidelens unit Gr1 is to the image side, the more excellently the anglecharacteristic matches with that of the dichroic film of the multi-colorseparation.,prism (e.g. three-color separation prism). In the case wherethe light incident on the object side lens unit Gr2 forms an angle tothe optical axis, the illuminance distribution deteriorates according tothe cosine fourth law. However, the object side lens unit Gr2 issubstantially telecentric to the object side and is thereforeadvantageous in preventing the illuminance distribution fromdeteriorating. Please note that the image side lens unit Gr1 and theobject side lens unit Gr2 are telecentric lens systems also in theabove-described first embodiment.

Third Embodiment

The third embodiment shown in FIGS. 9 to 11 has a more practicalarrangement than the first and second embodiments although its basicarrangement and advantages are the same as those of the above-describedsecond embodiment. The third embodiment includes a fewer number of lenselements. The image side lens unit Gr1 includes seven rotationallysymmetrical spherical lens elements and the object side lens unit Gr2includes six rotationally symmetrical spherical lens elements. Thisembodiment is suitable for color separation because the prism 2 and acover glass are provided on the side of the line CCD 3.

Tables 1 to 3 show construction data of the first to third embodiments(FIGS. 3 to 5, FIGS. 6 to 8, and FIGS. 9 to 11). In each table, Si (i=1,2, 3, . . . ) represents an ith surface counted from the object side, ri(i=1, 2, 3, . . . ) represents the radius of curvature of an ith surfaceSi counted from the object side, di (i=1, 2, 3, . . . ) represents anith axial distance counted from the object side, and Ni (i=1, 2, 3, . .. ) represents a refractive index (Nd) to the d-line of an ith lenscounted from the object side. These tables also show the focal length fof the entire lens system and the image side effective F-number EFFNO ata mirror rotation angle θ of 45 degrees (at this time, the object heightY=0). Table 4 shows mirror rotation angles θ (degrees) and correspondingobject heights Y (millimeters).

As described above, in the first to third embodiments, since the exitpupil of the object side lens unit Gr2 and the entrance pupil of theimage side lens unit Gr1 substantially coincide with each other,high-speed scanning without any curvature is achieved even when thesurface to be scanned is flat. In addition, since the object side lensunit Gr2 and the image side lens unit Gr1 are formed only ofrotationally symmetrical spherical lens elements which are inexpensiveand easy to manufacture, the cost is low. Therefore, by using thescanning optical system of the first to third embodiments, the cost ofthe scanning apparatus is effectively reduced. According to thearrangement of the first embodiment, since the size of the mirror isreduced, the size reduction of the scanning apparatus is effectivelyachieved. According to the arrangements of the second and thirdembodiments, since the illuminance distribution is prevented fromdeteriorating by the aperture diaphragm A, high-quality images areobtained where there is no nonuniformity of light quantity.

In the arrangement where the object side lens unit Gr2 and the imageside lens unit Gr1 each satisfy an image quality as an independent frontaperture lens system, a sufficient image quality is obtained with theentire scanning optical system, so that higher-quality images areobtained. Since the more telecentric the image side lens unit Gr1 is tothe image side, the more suitable the scanning optical system is forcolor separation, and the more telecentric the object side lens unit Gr2is to the object side, the more the illuminance distribution isprevented from deteriorating, high-quality images are obtained wherethere is further no nonuniformity of light quantity.

Additionally, in the first to third embodiments, since the ftanθ opticalsystem is used as the object side lens unit Gr2 so that the mainscanning speed increases as the light deflected by the mirror M in themain scanning becomes farther away from the optical axis, high-speedscanning without any distortion is achieved. Since a space for themirror M to rotate 360 degrees is provided between the object side lensunit Gr2 and the image side lens unit Gr1 so that the deflection for themain scanning is performed by rotating the mirror M, the biased loadimposed on the bearing of the mirror is reduced. Consequently, thebearing of the mirror M is prevented from being biasedly worn orpartially out of oil. Since it is unnecessary to use a driving apparatus(e.g. galvanic apparatus) for swingingly rotating the mirror M and adriving apparatus (e.g. a driving apparatus comprising a DC motor) whichis inexpensive and simple in structure may be used, the cost reductionand the simplification of the structure of the scanning apparatus areachieved.

Optical Arrangement Common to Fourth and Fifth Embodiments

FIG. 12 shows an x, y-z cross section (i.e. cross section in the subscanning direction) of the fourth embodiment developed in the directionsof the X- and Y-axes. In the figure, [T] shows the optical pathdeveloped in the directions of the X- and Y-axes at a high magnificationcondition (telephoto limit) and [W] shows that at a low magnificationcondition (wide angle limit). FIGS. 13 to 15 are x-y cross sections(i.e. cross sections in the main scanning direction) of the fifthembodiment. FIG. 13 shows the optical path at a mirror rotation angle(mirror swing angle) θ of 45 degrees (at this time, the object heightY=0). FIG. 14 shows the optical path at a mirror rotation angle θ of48.5 degrees. FIG. 15 shows the optical path at a mirror rotation angleθ of 41.5 degrees. In FIGS. 12 and 13, Si (i=1, 2, 3, . . . ) representsan ith surface counted from the object (film image plane 1) side.

In the fourth and fifth embodiments, the image side lens unit Gr1includes nine rotationally symmetrical spherical lens elements and theobject side lens unit Gr2 includes six rotationally symmetricalspherical lens elements. The mirror M is provided on the image side ofthe object side lens unit Gr2. The aperture diaphragm A is providedbetween the mirror M and the image side lens unit Gr1. The filter 2 isprovided on the image side of the image side lens unit Gr1 (on the sideof the line CCD 3). While the fourth and fifth embodiments are arrangedso that parallel light is incident on the mirror M, they may be arrangedso that convergent or divergent light is incident on the mirror M.

The lens elements included in the object side lens unit Gr2 have theiry-z cross sections formed circular so that the luminous flux is coveredwith respect to both the Y- and Z-axes. Similarly, the lens elementsincluded in the image side lens unit Gr1 have their x-z cross sectionsformed circular so that the luminous flux is covered with respect toboth the X- and Z-axes. However, to save the space in the scanningapparatus, it is desirable that the x-z cross section of the image sidelens unit Gr1 be elongated as mentioned previously because the luminousflux is necessarily covered only with respect to the sub scanningdirection (the direction of the Z-axis) which is the direction in whichthe light receiving devices of the line CCD 3 are arranged.

In the fourth and fifth embodiments, like in the first to thirdembodiments, the exit pupil of the object side lens unit Gr2 and theentrance pupil of the image side lens unit Gr1 substantially coincidewith each other. For this reason, the axial light and the off-axiallight having passed through the exit pupil of the object side lens unitGr2 are all incident on the entrance pupil of the image side lens unitGr1 and are all transmitted from the object side lens unit Gr2 to theimage side lens unit Gr1. Consequently, the axial light and theoff-axial light in the sub scanning direction deflected by the mirror Mare both imaged on the image side surface of the line CCD 3 by the imageside lens unit Gr1.

By thus arranging the lens system so that the exit pupil of the objectside lens unit Gr2 and the entrance pupil of the image side lens unitGr1 substantially coincide with each other, like in the first to thirdembodiments, the object side lens unit Gr2 and the image side lens unitGr1 constitute one lens system having a common pupil. The object sidelens unit Gr2 and the image side lens unit Gr1 each include onlyrotationally symmetrical spherical lens elements and have the field ofcurvature excellently corrected. Therefore, no curvature is caused inthe image plane with respect to the entire scanning optical system. Bythus forming the object side lens unit Gr2 and the image side lens unitGr1 of rotationally symmetrical spherical lens elements which areinexpensive and easy to manufacture, the cost reduction of the scanningapparatus is achieved. In addition, since the scanning optical systemincluding only spherical lens elements is simple in structure, therotation speed of the mirror M is readily increased. As a result, theimage of one frame of the 135 film is captured in approximately 0.2 toone second.

In the case where the main scanning of the film image plane 1 isperformed by deflecting the light with the mirror M, if the mirror Mfunctions as the aperture diaphragm for restricting the luminous flux,the projection changes with a change in angle between the mirror M andthe luminous flux. The quantity of the light incident on the image sidelens unit Gr1 changes with the change of the projection. For example,the quantity of the light received by the mirror M increases as themirror rotation angle θ increases, and conversely, the quantity of thelight received by the mirror M decreases as the mirror rotation angle θdecreases. Consequently, nonuniformity of light quantity is caused inthe image captured by the line CCD 3.

According to the arrangement of the fourth and fifth embodiments, likethe second and third embodiments, since the aperture diaphragm A isdisposed between the image side lens unit Gr1 and the mirror M, theluminous flux reflected without being restricted by the mirror M isrestricted by the aperture diaphragm A. Consequently, the quantity ofthe light incident on the image side lens unit Gr1 is uniform, so thatthe illuminance distribution (i.e. the illuminance distribution on theimage side surface of the line CCD 3) is prevented from deteriorating.In the case where the aperture diaphragm A is disposed between theobject side lens unit Gr2 and the mirror M, the luminous flux iseclipsed in the main scanning.

As described above, when the main scanning of the film image plane 1 isperformed by the mirror M, the optical path in the object side lens unitGr2 changes. That is, in the main scanning direction, even if the lightincident on the object side lens unit Gr2 is off-axial light, the lightis incident on the image side lens unit Gr1 as axial light. However,since the object side lens unit Gr2 and the image side lens unit Gr1each satisfy an image quality as an independent front aperture lenssystem with the aperture diaphragm A functioning as the front aperture,a sufficient image quality is obtained with the entire scanning opticalsystem.

The image side lens unit Gr1 is substantially telecentric to the imageside and is therefore suitable for an arrangement where a line sensorsuch as a multi-plate (e.g. three-plate) line CCD is used as the imagecapturing portion. This is because the more telecentric the image sidelens unit Gr1 is to the image side, the more excellently the anglecharacteristic matches with that of the dichroic film of the multi-colorseparation prism (e.g. three-color separation prism). In the case wherethe light incident on the object side lens unit Gr2 forms an angle tothe optical axis, the illuminance distribution deteriorates according tothe cosine fourth power law. However, the object side lens unit Gr2 issubstantially telecentric to the object side and is thereforeadvantageous in preventing the illuminance distribution fromdeteriorating.

Fourth Embodiment

The fourth embodiment is characterized in that a zoom optical system isused as the image side lens unit Gr1 in which the optical path does notchange in the main scanning. In the fourth embodiment, a zoom opticalsystem having three zoom units GrA, GrB and GrC is used as the imageside lens unit Gr1. Zooming is performed by moving the zoom units GrA,GrB and GrC in the direction of the optical axis AX. In FIG. 12, arrowsmA, mB and mC show movements for zooming of the zoom units GrA, GrB andGrC from the high magnification condition [T] to the low magnificationcondition [W].

According to the arrangement of the present scanning optical system, theaxial light and the off-axial light in the sub scanning direction areboth imaged on the image side surface of the line CCD 3 and the zoomoptical system used as the image side lens unit Gr1 forms imagesenlarged or reduced in the sub scanning direction (the direction of theZ-axis) on the image side surface of the line CCD 3 through zooming, sothat zooming only in the sub scanning direction (the direction of theZ-axis) is achieved (i.e. anisotropic magnification is achieved). Sincezooming is performed by the zoom optical system, the conjugate distancenever changes in the zooming. Therefore, by using the present scanningoptical system, the size of the scanning apparatus is effectivelyreduced. In addition, since the optical path does not change in the mainscanning in the image side lens unit Gr1 which is a zoom optical system,the luminous flux is not restricted in the main scanning.

Since it is unnecessary to process afterwards the images formed on theimage side surface of the line CCD 3 (i.e. captured images), imagesenlarged or reduced in the sub scanning direction are easily obtained.Consequently, convenience increases and the captured images are flexiblytreated. Because of the simple arrangement where the zoom optical systemformed of inexpensive and easily manufactured rotationally symmetricalspherical lens elements is used as the image side lens unit Gr1, byusing the present scanning optical system, the cost of the scanningapparatus is effectively reduced.

Fifth Embodiment

The fifth embodiment is characterized in that the speed of the mainscanning by the mirror M is set constant and changeable. The mainscanning of the film image plane 1 at the high magnification condition[T] is performed by rotating the mirror M in the main scanning range ofθ=41.5 to 48.5 degrees. Zooming is performed by changing the speed ofthe main scanning.

According to the arrangement of the present scanning optical system,since the speed and range of the main scanning by the mirror M ischangeable, zooming only in the main scanning direction (the directionof the- Y-axis) is achieved (i.e. anisotropic magnification is achieved)by setting desired main scanning speed and range. For example, enlargedimages are captured by setting the scanning speed to be low, andconversely, reduced images are captured by setting the main scanningspeed to be high.

Since the main scanning speed is changed by changing the rotationangular velocity of the mirror M, the main scanning speed is set bysetting the rotation angular velocity of the mirror M. The main scanningrange is set by setting the rotation range of the mirror M. Thus, themain scanning speed and the main scanning range are controlled only bycontrolling the rotation of the mirror M. Since the main scanning speedto be controlled is constant, there is no distortion in the mainscanning direction in the obtained image. This is because no distortionis caused in the main scanning direction if the main scanning speed isset constant by controlling the rotation angular velocity of the mirrorM.

Since it is unnecessary to process afterwards the images formed on theimage side surface of the line CCD 3 (i.e. captured images), imagesenlarged or reduced in the main scanning direction are easily obtained.Consequently, convenience increases and the captured images are flexiblytreated. Because of the simple arrangement where the lens units Gr1 andGr2 are formed of inexpensive and easily manufactured rotationallysymmetrical spherical lens elements and zooming in the main scanningdirection is performed only by controlling the rotation of the mirror,by using the present scanning optical system, the cost of the scanningapparatus is effectively reduced.

Combination of Fourth and Fifth Embodiments

The above-described zooming arrangements of the fourth and fifthembodiments may be combined so that the zooming operations aresimultaneously performed. By simultaneously performing the zooming inthe sub scanning direction by use of the zoom optical system in thefourth embodiment and the zooming in the main scanning direction bycontrolling the main scanning speed in the fifth embodiment, zooming isperformed in both the main and sub scanning directions, andisotropic/anisotropic magnification and high magnification aresimultaneously achieved.

Table 5 shows construction data of the fourth and fifth embodiments(FIGS. 12 to 15). In each table, Si (i=1, 2, 3, . . . ) represents anith surface counted from the object side, ri (i=1, 2, 3, . . . )represents the radius of curvature of an ith surface Si counted from theobject side, di (i=1, 2, 3, . . . ) represents an ith axial distancecounted from the object side, and Ni (i=1, 2, 3, . . . ) represents arefractive index (Nd) to the d-line of an ith lens counted from theobject side.

In the table, the axial distances varied during zooming are actual axialdistances among the zoom lens units GrA, GrB and GrC at the highmagnification condition [T], at the middle magnification (middle focallength) condition [M] and at the low magnification condition [W]. Table5 also shows the focal lengths f and the magnifications β of the entirelens system corresponding to the conditions [T], [M] and [W] and theimage side effective F-number EFFNO at a focal length f of 79.767 in thesub scanning direction (i.e. the direction of the Z-axis). Table 6 showsmirror rotation angles θ (degrees) and corresponding object heights Y(millimeters) in the main scanning direction in the fifth embodiment.

As described above, according to the fourth and fifth embodiments, likethe first to third embodiments, high-speed scanning without anycurvature is achieved even if the surface to be scanned is flat, and thecost reduction of the scanning apparatus is effectively achieved.According to the fourth embodiment, because of the simple arrangementwhere zooming in the sub scanning direction is performed by using a zoomoptical system as either of the object side lens unit Gr2 and the imageside lens unit Gr1 in which the optical path does not change in the mainscanning direction, zooming in the sub scanning direction is achieved atlow cost without resulting in an increase in size of the scanningoptical system. According to the fifth embodiment, because of the simplearrangement where zooming in the main scanning direction is performed bysetting the rotation speed and the rotation range of the mirror M to bechangeable, zooming in the main scanning direction is achieved at lowcost without resulting in an increase in size of the scanning opticalsystem.

Additionally, according to the fourth and fifth embodiments, since it isunnecessary to process the images captured at the image side surface,convenience increases and the captured images are flexibly treated.According to the combination of the fourth and fifth embodiments, sincezooming in both the main and sub scanning directions is achieved, andisotropic/anisotropic magnification and high magnification aresimultaneously achieved, the captured images are more flexibly treated.

Next, a scanning apparatus provided with a lens unit SL (FIGS. 18 to 20)according to sixth to eighth embodiments will be described withreference to the drawings. FIGS. 16A to 16C schematically show thearrangement of the scanning apparatus. In the figures, the X-axis, theY-axis and the Z-axis are axes perpendicular to one another. The X-axisis in parallel with the central axis AX1 of a film image plane 1 and theoptical axis AX2 of the lens unit SL. The Y-axis is in parallel with themain scanning direction. The Z-axis is in parallel with the sub scanningdirection.

As shown in FIGS. 16A to 16C, on a line CCD 12, the image of the filmimage plane 11 is formed by the lens unit SL. For example, when thecentral axis AX1 of the film image plane 11 and the optical axis AX2 ofthe lens unit SL coincide with each other, as is apparent from theoptical path at the cross section in the main scanning direction shownin FIG. 16A and the optical path at the cross section in the subscanning direction shown in FIG. 16C, the image of the central portionof the film image plane 11 is formed on the line CCD 12. By the line CCD12 having its light receiving devices arranged in the direction of theZ-axis (i.e. in the sub scanning direction), an image of one line in thesub scanning direction is captured as image information.

Main scanning for image capture is achieved by moving the image of thecentral portion of the film image plane 1 on the line CCD 12. Inconventional scanning apparatuses, main scanning for image capture isperformed by the above-described swinging rotation of the mirror. On thecontrary, in the present scanning apparatus, main scanning for imagecapture is performed by moving the lens unit SL vertically to theoptical axis AX2. Since the lens unit SL may be moved in any manner asfar as it is moved relatively to the film image plane 11 and to the lineCCD 12, main scanning for image capture is also achieved by moving thefilm image plane 11 and the line CCD 12 vertically to the optical axisAX2.

FIG. 16B shows the optical path when the lens. unit SL is movedvertically to the optical axis AX2 by a movement amount a. In this case,the image of the film image plane located a movement amount b (i.e.object height) away from the center of the film image plane 11 is formedon the line CCD 12. The relationship between the position of the lensunit SL and the position of the image of the film image plane 11 imagedon the line CCD 12 is represented by the following expression (1) by useof the movement amounts a and b of the positions from the conditionshown in FIGS. 16A and 16C:

b=(1+β)×a  (1)

where a is the movement amount of the lens unit SL (i.e. the distancefrom the central axis AX1 of the film image plane 11 to the optical axisAX2 of the lens unit SL), b is the movement amount of the position ofthe image on the film image plane 11 captured by the line CCD 12, and fis the magnification of the lens unit SL.

From the expression (1), it is understood that the movement amount b ofthe position of the image on the film image plane 11 captured by theline CCD 12 increases as the magnification β of the lens unit SLincreases. Therefore, when a film image plane 11 of a predetermined sizeis scanned, the greater the magnification β of the lens unit SL is, thesmaller the necessary movement amount a of the lens unit SL is. Becausethe smaller the movement amount a of the lens unit SL is, the moreeasily the speed of image information capture is increased, it.,isdesirable to use in the present scanning apparatus a lens unit SL havinga magnification β as high as possible. By thus selecting a lens unit SLhaving an appropriate magnification β, for example, the image of oneframe of the 135 film is captured in one to five seconds. In addition,since an inexpensive spherical lens system may be used as the lens unitSL and the movement of the lens unit SL is linear, the cost reduction ofthe scanning apparatus is achieved.

FIGS. 17A to 17C show the positions of the image on the film image plane11 captured by the line CCD 12 when the scanning apparatus of FIGS. 16Ato 16C is a unity magnification system (β=1). Reference numeral 13 is animage plane. Since this is a unity magnification system, b=2×a accordingto the expression (1). Therefore, the movement amount m of the lens unitSL is necessarily half the size (i.e. main scanning range) Ymax of thefilm image plane 11 to be captured (m=Ymax/2).

To obtain an excellent image quality from the center to the corner ofthe film image plane 11, it is desirable to use a lens unit SL realizingan excellent image quality. The lens construction of such a lens unit SLwill be described later in detail.

It is desirable that the lens unit SL be telecentric or substantiallytelecentric to the side of the line CCD 12. In that case, the advantageis obtained that when a line CCD 12 such as a multi-plate (e.g.three-plate) CCD is used as the image capturing portion, the moretelecentric the lens unit SL is to the side of the line CCD 12, the moreexcellently the angle characteristic matches with that of the dichroicfilm of the multi-color separation prism (e.g. three-color separationprism).

It is desirable that the lens unit SL be telecentric or substantiallytelecentric to the side of the film image plane 11. In the case wherethe light incident on the lens unit SL forms an angle to the opticalaxis AX2, the illuminance distribution deteriorates according to thecosine fourth law. In the case where an illumination system is used, theilluminance distribution also deteriorates due to a variation inmatching with the illumination system caused by the movement of the lensunit SL. The more telecentric the lens unit SL is to the side of thefilm image plane 11, the more advantageous the scanning apparatus is inpreventing the illuminance distribution from deteriorating.

While the line CCD 12 is used as the image capturing portion in theabove-described scanning apparatus, another type of line sensor may beused as the image capturing portion instead of the line CCD 12, or aphotoreceptor drum may be used as the image capturing portion. In thecase where a photoreceptor drum is used, the photoreceptor drum isdisposed so that its generatrix is in parallel with the sub scanningdirection.

While the above-described scanning apparatus is suitable for use as afilm scanner, the scanning apparatus of the present invention may beused as other types of scanning apparatuses. For example, instead of theline CCD 12, an apparatus (e.g. an LED array or a transmission-type LCDpanel) may be disposed which emits light including image information,and instead of the film image plane 11, a light receiving apparatus(e.g. an area CCD or a plane-form photoreceptor) may be provided whichreceives, reads and records light including image information.

Tables 7 to 9 show construction data of the sixth to eighth embodiments.In each table, Si (i=1, 2, 3, . . . ) represents an ith surface countedfrom the object side, ri (i=1, 2, 3, . . . ) represents the radius ofcurvature of an ith surface Si counted from the object side, di (i=1, 2,3, . . . ) represents an ith axial distance counted from the objectside, and Ni (i=1, 2, 3, . . . ) represents a refractive index (Nd) tothe d-line of an ith lens counted from the object side. These tablesalso show the focal length f and the magnification β of the entire lenssystem, the image side effective F-number EFFNO, and the object distanceS1.

Table 10 shows with respect to the lens unit SL of each of the sixth toeighth embodiments the movement amount b (millimeters) of the positionof the image of the film image plane 11 captured by the line CCD 12 whenthe lens unit SL is moved by the movement amount a (millimeters) fromthe central axis AX1 of the film image plane 11 vertically to theoptical axis AX2.

FIGS. 18 to 20 show lens arrangements of the lens units SL of the sixthto eighth embodiments, respectively. In the figures, Y is the objectheight (millimeters). Hereinafter, the lens arrangements of the sixth toeighth embodiments will be described.

In the sixth embodiment, the lens unit SL has, from the object (filmimage plane 11) side, a positive meniscus lens convex to the image side,a positive bi-convex lens, two positive meniscus lenses convex to theobject side, a negative meniscus lens concave to the image side, anaperture diaphragm A, a negative meniscus lens concave to the objectside, two positive meniscus lenses convex to the image side, a positivebi-convex lens, a positive meniscus lens convex to the object side, anda filter.

In the seventh embodiment, the lens unit SL has, from the object (filmimage plane 11) side, two positive bi-convex lenses, two positivemeniscus lenses convex to the object side, a negative meniscus lensconcave to the image side, an aperture diaphragm A, a negative meniscuslens concave to the object side, two positive meniscus lenses convex tothe image side, two positive bi-convex lenses, and a filter.

In the eighth embodiment, the lens unit SL has, from the object (filmimage plane 11) side, three positive meniscus lenses convex to theobject side, a negative meniscus lens concave to the image side, anaperture diaphragm A, a negative meniscus lens concave to the objectside, a positive meniscus lens convex to the image side, a positivebi-convex lens, a positive meniscus lens convex to the object side, anda filter.

As described above, the lens units SL of the sixth and seventhembodiments have five spherical lens elements on each side of theaperture diaphragm A, and one filter. The lens unit SL of the eighthembodiment has four spherical lens elements on each side of the aperturediaphragm A, and one filter. The lens units SL of the sixth to eighthembodiments all adopt a symmetrical structure which is advantageous incorrecting aberration such as distortion with respect to the off-axiallight. For this reason, the lens units SL of these embodiments realizean excellent image quality although they are formed of inexpensivespherical lens elements. In addition, since the lens units SL aretelecentric or substantially telecentric to the object side and to theimage side, as mentioned above, the angle characteristic excellentlymatches with that of the dichroic film and the illuminance distributionis effectively prevented from deteriorating.

As described above, according to the scanning optical systems of thesixth to eighth embodiments, scanning for image capture is achieved onlyby slightly moving the lens units. As a result, images are captured athigh speed. In addition, since no mirror is necessary, the size of thelens unit is reduced. As a result, the size reduction of the scanningapparatus is achieved.

Obviously, many modifications and variations of the present inventionare possible in light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims, the inventionmay be practiced other than as specifically described.

TABLE 1 << Construction Data of Embodiment 1 >> f = 94.638, EFFNO = 7.91Radius of Axial Refractive Surface Curvature Distance Index S1  r1 =−39.807 d1 = 4.000 N1 = 1.58913 S2  r2 = −224.184 d2 = 10.000 N2 =1.58144 S3  r3 = −73.550 d3 = 3.000 S4  r4 = −66.229 d4 = 10.000 N3 =1.67000 S5  r5 = −64.550 d5 = 0.620 S6  r6 = 1212.327 d6 = 10.000 N4 =1.67000 S7  r7 = −105.642 d7 = 0.620 S8  r8 = 89.376 d8 = 8.560 N5 =1.67000 S9  r9 = −3435.010 d9 = 0.620 S10 r10 = 43.766 d10 = 12.000 N6 =1.51680 S11 r11 = 48732.943 d11 = 3.750 N7 = 1.80518 S12 r12 = 39.567d12 = 9.000 S13 r13 = −67.327 d13 = 4.000 N8 = 1.67000 S14 r14 =−115.029 d14 = 14.500 S15 r15 = −134.934 d15 = 2.500 N9 = 1.80518 S16r16 = −72.443 d16 = 20.000 S17 r17 = ∞ (Mirror M) d17 = 20.000 S18 r18 =72.443 d18 = 2.500 N10 = 1.80518 S19 r19 = 134.934 d19 = 14.500 S20 r20= 115.029 d20 = 4.000 N11 = 1.67000 S21 r21 = 67.327 d21 = 9.000 S22 r22= −39.567 d22 = 3.750 N12 = 1.80518 S23 r23 = −48732.943 d23 = 12.000N13 = 1.51680 S24 r24 = −43.766 d24 = 0.620 S25 r25 = 3435.010 d25 =8.560 N14 = 1.67000 S26 r26 = −89.376 d26 = 0.620 S27 r27 = 105.642 d27= 10.000 N15 = 1.67000 S28 r28 = −1212.327 d28 = 0.620 S29 r29 = 64.550d29 = 10.000 N16 = 1.67000 S30 r30 = 66.229 d30 = 3.000 S31 r31 = 73.550d31 = 10.000 N17 = 1.58144 S32 r32 = 224.184 d32 = 4.000 N18 = 1.58913S33 r33 = 39.807

TABLE 2 << Construction Data of Embodiment 2 >> f = 68.239, EFFNO = 3.49Radius of Axial Refractive Surface Curvature Distance Index S1  r1 =−34.552 d1 = 4.000 N1 = 1.51680 S2  r2 = −1136.364 d2 = 10.000 N2 =1.61659 S3  r3 = −135.073 d3 = 3.000 S4  r4 = −82.721 d4 = 10.000 N3 =1.67000 S5  r5 = −50.877 d5 = 0.620 S6  r6 = −1145.869 d6 = 10.000 N4 =1.67000 S7  r7 = −125.677 d7 = 0.620 S8  r8 = 85.317 d8 = 8.560 N5 =1.67000 S9  r9 = 451.284 d9 = 0.620 S10 r10 = 46.069 d10 = 12.000 N6 =1.51680 S11 r11 = −119.753 d11 = 3.750 N7 = 1.80518 S12 r12 = 47.78 d12= 9.000 S13 r13 = −41.217 d13 = 4.000 N8 = 1.67000 S14 r14 = −62.455 d14= 4.000 S15 r15 = −93.171 d15 = 2.500 N9 = 1.80518 S16 r16 = −47.299 d16= 18.000 S17 r17 = ∞ (Mirror M) d17 = 17.000 S18 r18 = ∞ (ApertureDiaphragm A) d18 = 1.000 S19 r19 = 42.128 d19 = 1.550 N10 = 1.84666 S20r20 = 99.150 d20 = 8.990 S21 r21 = 200.000 d21 = 2.480 N11 = 1.67000 S22r22 = 38.462 d22 = 5.580 S23 r23 = −22.073 d23 = 2.325 N12 = 1.80518 S24r24 = 217.771 d24 = 7.440 N13 = 1.51680 S25 r25 = −28.733 d25 = 0.384S26 r26 = −431.654 d26 = 5.307 N14 = 1.67000 S27 r27 = −35.664 d27 =0.384 S28 r28 = 96.281 d28 = 6.200 N15 = 1.67000 S29 r29 = 2927.315 d29= 0.384 S30 r30 = 37.345 d30 = 6.200 N16 = 1.67000 S31 r31 = 44.920 d31= 1.860 S32 r32 = 45.893 d32 = 6.200 N17 = 1.58144 S33 r33 = 123.964 d33= 2.480 N18 = 1.58913 S34 r34 = 32.678 d34 = 30.000 S35 r35 = ∞ d35 =20.600 N19 = 1.74400 S36 r36 = ∞ (Prism 2) d36 = 0.800 N20 = 1.51680 S37r37 = ∞ (Prism 2)

TABLE 3 << Construction Data of Embodiment 3 >> f = 88.399, EFFNO = 4.99Radius of Axial Refractive Surface Curvature Distance Index S1  r1 =−49.542 d1 = 4.000 N1 = 1.61659 S2  r2 = 844.495 d2 = 10.000 S3  r3 =−630.064 d3 = 8.000 N2 = 1.61800 S4  r4 = −83.652 d4 = 1.000 S5  r5 =186.095 d5 = 8.000 N3 = 1.61800 S6  r6 = −186.302 d6 = 0.620 S7  r7 =70.451 d7 = 7.000 N4 = 1.61800 S8  r8 = 312.890 d8 = 2.620 S9  r9 =36.382 d9 = 8.000 N5 = 1.69100 S10 r10 = 76.584 d10 = 4.000 N6 = 1.66446S11 r11 = 26.274 d11 = 33.000 S12 r12 = ∞ (Mirror M) d12 = 12.000 S13r13 = ∞ (Aperture Diaphragm A) d13 = 4.500 S14 r14 = 30.560 d14 = 5.500N7 = 1.78831 S15 r15 = −51.112 d15 = 2.200 N8 = 1.54072 S16 r16 =143.776 d16 = 8.000 S17 r17 = −33.178 d17 = 3.000 N9 = 1.75520 S18 r18 =30.510 d18 = 7.200 S19 r19 = −63.595 d19 = 5.000 N10 = 1.68150 S20 r20 =−36.559 d20 = 1.000 S21 r21 = 79.252 d21 = 9.000 N11 = 1.71700 S22 r22 =−34.900 d22 = 3.800 S23 r23 = −34.526 d23 = 2.800 N12 = 1.61659 S24 r24= 107.174 d24 = 3.000 S25 r25 = 90.113 d25 = 7.000 N13 = 1.69680 S26 r26= −90.481 d26 = 16.000 S27 r27 = ∞ d27 = 20.000 N14 = 1.74400 (Prism 2)S28 r28 = ∞ d28 = 2.400 N15 = 1.51680 (Prism 2) S29 r29 = ∞ d29 = 0.500S30 r30 = ∞ d30 = 0.800 N16 = 1.51680 (Cover Glass) S31 r31 = ∞

TABLE 4 Mirror Rotation Object Height Y (mm) Angle ⊖ (°) Emb. 1 Emb. 2Emb. 3 40 17.63 17.72 17.57 41 14.05 14.10 14.02 42 10.51 10.53 10.50 436.99 7.0 6.99 44 3.49 3.50 3.49 45 0 0 0 46 −3.49 −3.50 −3.49 47 −6.99−7.00 −6.99 48 −10.51 −10.53 −10.50 49 −14.05 −14.10 −14.02 50 −17.63−17.72 −17.57

TABLE 5 << Construction Data of Embodiments 4 and 5 >> f =79.767˜63.447˜53.974 β = −0.669˜−0.558˜−0.478 EFFNO = 5.21 Radius ofAxial Refractive Surface Curvature Distance Index S1  r1 = −49.542 d1 =4.000 N1 = 1.61659 S2  r2 = 844.495 d2 = 10.000 S3  r3 = −630.064 d3 =8.000 N2 = 1.61800 S4  r4 = −83.652 d4 = 1.000 S5  r5 = 186.095 d5 =8.000 N3 = 1.61800 S6  r6 = −186.302 d6 = 0.620 S7  r7 = 70.451 d7 =7.000 N4 = 1.61800 S8  r8 = 312.890 d8 = 2.620 S9  r9 = 36.382 d9 =8.000 N5 = 1.69100 S10 r10 = 76.584 d10 = 4.000 N6 = 1.66446 S11 r11 =26.274 d11 = 33.000 S12 r12 = ∞ (Mirror M) d12 = 12.000 S13 r13 = ∞(Aperture Diaphragm A) d13 = 0.500˜11.411˜16.648 S14 r14 = 18.893 d14 =4.100 N7 = 1.76200 S15 r15 = 99.555 d15 = 1.500 S16 r16 = −55.909 d16 =4.800 N8 = 1.75520 S17 r17 = 20.006 d17 = 1.800 S18 r18 = 51.415 d18 =2.600 N9 = 1.74350 S19 r19 = −45.455 d19 = 0.900 S20 r20 = −213.315 d20= 2.600 N10 = 1.78100 S21 r21 = −56.193 d21 = 1.800˜6.580˜11.189 322 r22= 46.974 d22 = 3.200 N11 = 1.75690 S23 r23 = −28.957 d23 = 1.200 S24 r24= −29.053 d24 = 1.000 N12 = 1.65446 S25 r25 = 60.000 d25 = 2.000 S26 r26= −23.796 d26 = 1.100 N13 = 1.74000 S27 r27 = 54.165 d27 =21.500˜9.732˜2.347 S28 r28 = 55.316 d28 = 6.500 N14 = 1.74400 S29 r29 =−33.011 d29 = 1.700 N15 = 1.60342 S30 r30 = −323.724 d30 =8.425˜4.503˜2.040 S31 r31 = ∞ d31 = 3.000 N16 = 1.51680 (Filter 2) S32r32 = ∞ Σd = 168.465˜168.465˜168.465

TABLE 6 Mirror Rotation Object Height Y Angle ⊖ (°) (mm) 40 16.79 4113.40 42 10.04 43 6.68 44 3.34 45 0 46 −3.34 47 −6.68 48 −10.04 49−13.40 50 −16.79

TABLE 7 << Construction Data of Embodiment 6 >> f = 279.805, β = −1.000,EFFNO = 6.50, S1 = −76.83 Radius of Axial Refractive Surface CurvatureDistance Index S1  r1 = −167.383 d1 = 9.000 N1 = 1.51680 S2  r2 =−67.724 d2 = 0.251 S3  r3 = 379.082 d3 = 8.542 N2 = 1.51680 S4  r4 =−120.166 d4 = 0.251 S5  r5 = 41.277 d5 = 15.000 N3 = 1.51680 S6  r6 =207.734 d6 = 0.754 S7  r7 = 33.786 d7 = 11.557 N4 = 1.51680 S8  r8 =100.032 d8 = 3.517 S9  r9 = 294.632 d9 = 4.020 N5 = 1.75520 S10 r10 =21.879 d10 = 12.000 S11 r11 = ∞ (Aperture Diaphragm A) d11 = 12.000 S12r12 = −21.879 d12 = 4.020 N6 = 1.75520 S13 r13 = −294.632 d13 = 3.517S14 r14 = −100.032 d14 = 11.557 N7 = 1.51680 S15 r15 = −33.786 d15 =0.754 S16 r16 = −207.734 d16 = 15.000 N8 = 1.51680 S17 r17 = −41.277 d17= 0.251 S18 r18 = 120.166 d18 = 8.542 N9 = 1.51680 S19 r19 = −379.082d19 = 0.251 S20 r20 = 67.724 d20 = 9.000 N10 = 1.51680 S21 r21 = 167.383d21 = 28.747 S22 r22 = ∞ d22 = 0.533 N11 = 1.51680 (Filter) S23 r23 = ∞

TABLE 8 << Construction Data of Embodiment 7 >> f = 1013.340, β =−10.000, EFFNO = 6.50, S1 = −93.08 Radius of Axial Refractive SurfaceCurvature Distance Index S1  r1 = 323.390 d1 = 9.000 N1 = 1.61800 S2  r2= −123.393 d2 = 0.251 S3  r3 = 1852.813 d3 = 8.542 N2 = 1.49310 S4  r4 =−165.032 d4 = 0.251 S5  r5 = 41.372 d5 = 13.000 N3 = 1.49310 S6  r6 =235.114 d6 = 0.754 S7  r7 = 38.542 d7 = 11.557 N4 = 1.61800 S8  r8 =68.177 d8 = 3.517 S9  r9 = 247.646 d9 = 4.020 N5 = 1.74000 S10 r10 =22.919 d10 = 20.000 S11 r11 = ∞ (Aperture Diaphragm A) d11 = 20.000 S12r12 = −22.919 d12 = 4.020 N6 = 1.74000 S13 r13 = −247.646 d13 = 3.517S14 r14 = −68.177 d14 = 11.557 N7 = 1.61800 S15 r15 = −38.542 d15 =0.754 S16 r16 = −235.114 d16 = 13.000 N8 = 1.49310 S17 r17 = −41.372 d17= 0.251 S18 r18 = 165.032 d18 = 8.542 N9 = 1.49310 S19 r19 = −1852.813d19 = 0.251 S20 r20 = 123.393 d20 = 9.000 N10 = 1.61800 S21 r21 =−323.390 d21 = 28.747 S22 r22 = ∞ d22 = 0.533 N11 = 1.51680 (Filter) S23r23 = ∞

TABLE 9 << Construction Data of Embodiment 8 >> f = 127.221, β = −0.700,EFFNO = 6.19, S1 = −162.24 Radius of Axial Refractive Surface CurvatureDistance Index S1  r1 = 53.257 d1 = 9.887 N1 = 1.61800 S2  r2 = 1073.295d2 = 0.241 S3  r3 = 44.130 d3 = 6.752 N2 = 1.49310 S4  r4 = 66.381 d4 =2.170 S5  r5 = 37.975 d5 = 9.164 N3 = 1.49310 S6  r6 = 124.632 d6 =1.929 S7  r7 = 494.025 d7 = 3.858 N4 = 1.61950 S8  r8 = 20.134 d8 =16.157 S9  r9 = ∞ (Aperture Diaphragm A) d9 = 20.015 S10 r10 = −25.500d10 = 3.858 N5 = 1.72100 S11 r11 = −119.847 d11 = 2.411 S12 r12 =−103.498 d12 = 11.093 N6 = 1.61800 S13 r13 = −31.806 d13 = 1.929 S14 r14= 10529.641 d14 = 8.500 N7 = 1.49310 S15 r15 = −61.224 d15 = 0.241 S16r16 = 126.783 d16 = 7.234 N8 = 1.61800 S17 r17 = 921.073 d17 = 57.209S18 r18 = ∞ d18 = 1.061 N9 = 1.51680 (Filter) S19 r19 = ∞

TABLE 10 a (mm) −10 −5 0 5 10 b (mm) Emb. 6 −20 −10 0 10 20 Emb. 7 −20−10 0 10 20 Emb. 8 −17 −8.5 0 8.5 17

What is claimed is:
 1. A scanning optical system comprising: an objectside lens unit; a rotatable deflector for deflecting light passingthrough the object side lens unit to perform scanning for taking in aprimary image formed on an object side surface, said deflector beingdisposed in a vicinity of an exit pupil of the object side lens unit,and said deflector being a plane mirror having a deflecting surfacelying on a rotational axis of the mirror; and an image side lens unitfor focusing on an image side surface both axial and off-axial rays withrespect to a sub-scanning direction, said image side lens unit beingprovided so that an entrance pupil thereof substantially coincides withan exit pupil of the object side lens unit, wherein in a case where anaperture diaphragm is disposed in a position of the coinciding pupils,the object side lens unit and the image side lens unit each satisfy animage quality as a front aperture lens when they are regarded asindependent lens units with a side of the aperture diaphragm as anobject side.
 2. A scanning optical system as claimed in claim 1, whereinsaid image side lens unit is telecentric or substantially telecentric toan image side.
 3. A scanning optical system as claimed in claim 1,wherein said object side lens unit is telecentric or substantiallytelecentric to an object side.
 4. A scanning optical system as claimedin claim 1, wherein said mirror is rotatable 360 degrees.
 5. A scanningoptical system comprising: an object side lens unit; a rotatabledeflector for deflecting light passing through the object side lens unitto perform scanning for taking in a primary image formed on an objectside surface, said deflector being disposed in a vicinity of an exitpupil of the object side lens unit, and said deflector being a planemirror having a deflecting surface lying on a rotational axis of themirror; and an image side lens unit for focusing on an image sidesurface both axial and off-axial rays with respect to a sub-scanningdirection, said image side lens unit being provided so that an entrancepupil thereof substantially coincides with an exit pupil of the objectside lens unit, wherein of the object side lens unit and the image sidelens unit, the lens unit in which an optical path changes in a mainscanning direction is a lens unit of an ftanθ projection method, saidmain scanning direction being a direction in which the light isdeflected by a rotation of the mirror, and wherein a rotation speed ofthe plane mirror is changed so that a main scanning speed increases asthe light becomes farther away from an optical axis in a main scanning.6. A scanning optical system comprising: an object side lens unit; arotatable deflector for deflecting light passing through the object sidelens unit to perform scanning for taking in a primary image formed on anobject side surface, said deflector being disposed in a vicinity of anexit pupil of the object side lens unit, and said deflector being aplane mirror having a deflecting surface lying on a rotational axis ofthe mirror; and an image side lens unit for focusing on an image sidesurface both axial and off-axial rays with respect to a sub-scanningdirection, said image side lens unit being provided so that an entrancepupil thereof substantially coincides with an exit pupil of the objectside lens unit, wherein of the object side lens unit and the image sidelens unit, the lens unit in which an optical path does not change in amain scanning direction is a zoom lens system, said main scanningdirection being a direction in which the light is deflected by arotation of the plane mirror.
 7. A scanning optical system comprising:an object side lens unit; a rotatable deflector for deflecting lightpassing through the object side lens unit to perform scanning for takingin a primary image formed on an object side surface, said deflectorbeing disposed in a vicinity of an exit pupil of the object side lensunit, and said deflector being a plane mirror having a deflectingsurface lying on a rotational axis of the mirror; and an image side lensunit for focusing on an image side surface both axial and off-axial rayswith respect to a sub-scanning direction, said image side lens unitbeing provided so that an entrance pupil thereof substantially coincideswith an exit pupil of the object side lens unit, wherein a rotationspeed of the plane mirror is changeable.
 8. A scanning optical systemcomprising: an object side lens unit; a rotatable deflector fordeflecting light passing through the object side lens unit to performscanning for taking in a primary image formed on an object side surface,said deflector being disposed in a vicinity of an exit pupil of theobject side lens unit, and said deflector being a plane mirror having adeflecting surface lying on a rotational axis of the mirror; and animage side lens unit for focusing on an image side surface both axialand off-axial rays with respect to a sub-scanning direction, said imageside lens unit being provided so that an entrance pupil thereofsubstantially coincides with an exit pupil of the object side lens unit,wherein in a case where an aperture diaphragm is disposed in a positionof the coinciding pupils, the object side lens unit, wherein of theobject side lens unit and the image side lens unit, the lens unit inwhich an optical path does not change in a main scanning direction is azoom lens system, said main scanning direction being a direction inwhich the light is deflected by a rotation of the plane mirror, andwherein a rotation speed of the plane mirror is changeable.